'Cold turkey' only option for Karachi's addicts
In Pakistan's largest city Karachi, heroin is cheaper than food and there are a vast number of drug addicts.
Those who want to break their habit often go to a rehabilitation centre run by a charity called the Edhi Foundation.
The foundation cares for about 4,500 patients at any one time, but treatment is basic and without the resources to provide drugs such as methadone, patients at the clinic have to go "cold turkey" with only sedative injections and paracetamol tablets offered for pain relief.
Mobeen Azhar reports for BBC's Newsnight.